This is an unusual Cossor WR1 dual voltage directly heated triode. It is very similar to the P1 but is gettered and has a bakelite base. The unusual cup anode is believed to be a way of avoiding a Marconi patent on cylindrical anodes. It probably dates from 1924.
The additional screw side contact on the base allows the valve to be operated from a 4 or 6 volt heater supply. The conventional filament contacts are for 2 volt use.
The valve is engraved with the Cossor Trademark, the type - WR1, filament and anode operating voltages, 'Patent 7282-8/22' and 'No. 245'. The internal construction appears identical to the Cossor P1 at the National Valve Museum and to Dave's metal based version although this one has not been 'lit' so so I cannot tell if it is a dull emitter version. Here is an illustration of a very similar valve from the 1935-6 Cossor Valve Manual, where it was an historical exhibit.
